Urethral function after chronic cauda equina lesion in cats. II. The role of autonomically-innervated smooth and striated muscle in distal sphincter dysfunction.

We investigated the possibility that distal sphincter dysfunction after chronic sacral rhizotomy in the cat might be due to altered sympathetic influences on smooth and striated muscle. Three months after rhizotomy, sympathetic influences on basal perfusion pressure in the distal sphincteric urethra were significantly decreased. A prazosin-sensitive component of basal perfusion pressure remained after section of all extrinsic urethral innervation in both control and chronic cats. Local intra-arterial 6-hydroxydopamine also abolished this component. After rhizotomy, noradrenaline content in the distal sphincteric urethra was significantly increased but there was no evidence of a change in sensitivity to sympathetic stimulation. A novel prazosin- and atropine-resistant component of the response to hypogastric nerve stimulation was seen in the rhabdosphincteric urethra of chronic cats. This component was abolished by atracurium or hexamethonium. It was significantly greater in cats with S1-3 as compared to S2-3 lesions and was never seen in control cats. It is concluded that autonomic activation of the rhabdosphincter could be a factor in distal sphincter obstruction.